1. Field of the Invention
This invention relates generally to the treatment of oral mucositis and, more particularly, to methods for treating oral mucositis with a Reactive Oxygen Species (“ROS”) scavenger. The compositions and methods are useful in treating oral mucositis.
2. Description of Related Art
Oral ulcerative mucositis is a common, painful, dose-limiting toxicity of drug and radiation therapy for cancer (1). The disorder is characterized by breakdown of the oral mucosa that results in the formation of ulcerative lesions. In granulocytopenic patients, the ulcerations that accompany mucositis are frequent portals of entry for indigenous oral bacteria often leading to sepsis or bacteremia (2). Mucositis occurs to some degree in more than one third of patients receiving anti-neoplastic drug therapy (3). The frequency and severity are significantly greater among patients who are treated with induction therapy for leukemia or with many of the conditioning regimens for bone marrow transplant (4). Among these individuals, moderate to severe mucositis can occur in more than three-quarters of patients. Moderate to severe mucositis occurs in virtually all patients who receive radiation therapy for tumors of the head and neck and typically begins with cumulative exposures of 15 Gy and then worsens as total doses of 60 Gy or more are reached (1-4).
Clinically mucositis progresses through three stages:
1. Atrophic changes accompanied by painful mucosal erythema, which can respond to local anesthetics.
2. Painful ulceration with pseudomembrane formation and, in the case of myelosuppressive treatment, potentially life-threatening sepsis, requiring antimicrobial therapy. Pain is often of such intensity as to require parenteral narcotic analgesia.
3. Spontaneous healing, occurring about 2-3 weeks after cessation of anti-neoplastic therapy.
Standard therapy for mucositis is predominantly palliative, including application of topical analgesics such as lidocaine and/or systemic administration of narcotics and antibiotics. At present, the only approved treatment for oral mucositis is palifermin (Kepivance) which is a member of the fibroblast growth factor (FGF) superfamily of molecules. Palifermin's approval is limited to the treatment of oral mucositis in the patients undergoing conditioning regimens prior to hematopoietic stem cell transplants for the treatment of hematologic malignancies.
The complexity of mucositis as a biological process has only been recently appreciated (5-7). It has been suggested that the condition represents a sequential interaction of oral mucosal cells and tissues, reactive oxygen species, pro-inflammatory cytokines, mediators of apoptosis and local factors such as saliva and the oral microbiota. While epithelial degeneration and breakdown ultimately result in mucosal ulceration, it appears that the early changes associated with radiation-induced mucosal toxicity occur within the endothelium, and connective tissue of the submucosa. For example, electron microscopic evaluation of mucosa within 1 week of radiation shows damage to both endothelium and connective tissue, but not epithelium. It appears that the overall mechanism for mucositis development is similar for both radiation and chemotherapy (8).
Recently, a superoxide dismutase mimetic, M40403, was shown to be effective in an animal models of inflammation (Salvemini et al., Science 286:304-306, 1999) and, more specifically, in an animal model of rheumatoid arthritis (Salvemini et al., Arthritis & Reumatism 44:2909-2921, 2001). Nevertheless, treatment of oral mucositis using M40403 has neither been reported nor suggested.